As a system that detects the state of a secondary battery and controls the state, various ones have been proposed so far. Patent Literatures 1 to 3 disclose systems that sense the state of charge (the amount of storage or SOC) of a secondary battery based on the battery voltage of the secondary battery. Patent Literature 4 discloses a system that includes dV/dQ calculation means for calculating the value of dV/dQ, which is the proportion of the amount of change dV in the battery voltage V of a secondary battery to the amount of change dQ in the amount of storage Q, and senses the state of a secondary battery system utilizing a characteristic point appearing on a Q−dV/dQ curve representing the relationship between the value of the amount of storage Q and the value of dV/dQ, or a characteristic point appearing on a V−dV/dQ curve representing the relationship between the value of the battery voltage V and the value of dV/dQ.
On the other hand, Patent Literature 5 discloses a lithium secondary battery including a negative electrode using silicon oxide as a negative electrode active material.